Two objects of same class reference each other.

wolfv (222)
In the following example, obj1 and obj2 reference each other.
obj1 and obj2 are of the same class.
The compiler is giving me linker errors.

circular_dependency_other_obj.cpp:
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#include "CClass.h"

CClass obj1(1);
CClass obj2(2);

int main()
{
    obj1.begin(&obj2); //these two objects reference each other
    obj2.begin(&obj1);

    obj1.print();
    obj1.printOther();

    obj2.print();
    obj2.printOther();
}

CClass.h:
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#ifndef CLCASS_H
#define CLCASS_H

#include <iostream>

//class CClass; //forward declaration not needed

class CClass
{
    private:
	int id;
        CClass* ptrCClass;
    public:
	CClass(int id) : id(id) {}
        void begin(CClass* ptr);
        void printOther();
        void print();
};
#endif

CClass.cpp:
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#include "CClass.h"

void CClass::begin(CClass* ptr) { ptrCClass = ptr; }
void CClass::printOther() { ptrCClass->print(); }
void CClass::print() { std::cout << id << std::endl; }


Linker errors:
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$ g++ circular_dependency_other_obj.cpp
/tmp/ccXO0s4R.o: In function `main':
circular_dependency_other_obj.cpp:(.text+0xf): undefined reference to `CClass::begin(CClass*)'
circular_dependency_other_obj.cpp:(.text+0x1e): undefined reference to `CClass::begin(CClass*)'
circular_dependency_other_obj.cpp:(.text+0x28): undefined reference to `CClass::print()'
circular_dependency_other_obj.cpp:(.text+0x32): undefined reference to `CClass::printOther()'
circular_dependency_other_obj.cpp:(.text+0x3c): undefined reference to `CClass::print()'
circular_dependency_other_obj.cpp:(.text+0x46): undefined reference to `CClass::printOther()'
collect2: error: ld returned 1 exit status

What went wrong?
Last edited on
helios (17563)
You forgot to link the other .cpp.
g++ circular_dependency_other_obj.cpp CClass.cpp
wolfv (222)
Thanks helios, that worked:
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$ g++ circular_dependency_other_obj.cpp CClass.cpp 
$ ./a.out
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